In the construction sector, in which problems linked to the use of ever smaller spaces are constantly faced, up to now much use has been made of modular staircases, often classed as spiral staircases and flight staircases. Both indoors and outdoors these allow the connection of rooms at different heights, using spaces which may have an extremely small footprint, or which have particular shapes. Without sacrificing the necessary safety, in the production of modular staircases, and therefore of the steps of which they consist, there are known construction techniques which allow a certain adaptability to the height which the entire staircase must cover. Since such heights may be very different, it is evident that, if a first adaptation of the staircase may be achieved according to the number of steps, only the possibility of making precision adjustments to the rise between one step and another allows production of the steps to be standardised, so that the solution to any type of potential problem is ready. The materials used to produce the steps for this type of staircase are currently wood and various types of metal alloys. Using wood, the step is first shaped to give the tread the required shape, then the various steps are stacked alternating with spacers having standard height and keyed together with the spacers on a vertical pole which acts as a tie rod, so as to keep the steps connected and make the staircase able to withstand the stresses to which it is subjected during use.
In this case, the precision adjustment is made by adding separators with limited height, also made of wood or plastic, or in any event of a material strong enough to avoid significant deformation during use. These separators are inserted between a step and a spacer at one or more points of the vertical extension of the staircase, to give the staircase the required overall height.
If a metal alloy is used instead, it is first machined into the shape of a flat sheet with limited thickness, then drawn and bent to give the step the required shape. Then the edges are trimmed and the step is welded to a portion of tube which helps to cover the pole which acts as a tie rod. Finally, it is cleaned and painted to give it the predetermined appearance.
In this case too, precision adjustment may be carried out using a spacer consisting of two end ring nuts, also useful for centering the pole in the tube. Connected to one of the ring nuts is a smooth shank, on which a predetermined number of separators, similar to those previously described, may be inserted, to separate the two ring nuts, and so also two consecutive steps, by the required distance. Alternatively, a threaded shank may be integral with one of the two ring nuts. The other ring nut may be screwed onto the threaded shank, so as to make the adjustment by interrupting the screwing on action at the required point and without having to use the above-mentioned separators.
In both solutions, that is to say, whether using wood or metal alloys to produce the modular staircase, the elements used for the precision adjustment are at least partly visible, and this is often disadvantageous in terms of appearance, creating gaps in the shapes of the step, especially if the part visible comprises portions of the thread.
Moreover, at least if metal alloys are used, further processing is required, for example, painting, deburring and sandblasting, which in some cases may be carried out even after assembly and which in any event extend production times and increase costs.